1. Field of the Invention
The present invention relates generally to the firing of projectiles on a range, and, more particularly, to an apparatus and method for decelerating and trapping munitions fired on a range.
2. Background Description
In order to maintain proficiency in the use of firearms, it is common to engage in target practice on a training range. Traditionally, the primary concern on a training range was the prevention of ricochets. Thus, ranges often use a large dirt berm behind the target to decelerate and trap the bullet.
More recently, however, considerable concern has been raised about the environmental impact of heavy metals (e.g., lead, tungsten, copper) contained within the bullet. Though a bullet fired into a mound of dirt is safely contained from the standpoint of no longer being a dangerous projectile, heavy metals within the bullet remain free to leach into the soil, thereby contaminating the environment. Thus, shooting ranges have begun to stress containment and removal of expended rounds in order to prevent environmental contamination.
Additionally, there is a growing desire to build shooting ranges within enclosed structures. This permits frequent use of the range regardless of weather and without excessive travel time. Obviously, however, use of a dirt berm behind the target is impractical for such indoor ranges.
Thus, current trends in bullet containment systems focus on two different types of systems. The first, often called a bullet stop and containment chamber, has a pair of plates that channel bullets toward an opening in a containment chamber. Inside the containment chamber are impact plates that slow the bullet to a stop. Unfortunately, such systems are relatively expensive and difficult to manufacture and maintain.
The second type of containment system is the bullet backstop or bullet trap system. Bullet backstops typically include a back plate made of steel inclined to the line of fire. On an upper surface of the back plate, a layer of material is disposed to provide a medium for decelerating and trapping bullets. This layer is several feet thick in the direction the bullet travels. The impact material is typically a resilient granular material. As a bullet impacts the material, it will decelerate sufficiently such that, if it does impact the back plate, any ricochet will be minimal.
A number of bullet traps utilize rubber chunks or chips as the impact material. For example, U.S. Pat. No. 6,378,870 to Sovine (“the '870 Patent”) teaches the use of relatively large rubber nuggets disposed along a plane inclined to the line of fire, while U.S. Pat. No. 5,848,794 to Wojcinski et al. (“the '794 Patent”) discloses a similar bullet trap using relatively small rubber granules disposed along an inclined plane. To reduce scatter and sluffing of the impact material, the '794 Patent further teaches the use of a self-healing membrane covering the rubber granules.
However, trapping systems like those disclosed in the '870 Patent and the '794 Patent lack inherent fire retardant characteristics. Thus, they often suffer from heat and fire problems, especially if the chips are not treated with a fire retardant, are improperly maintained, contain steel or fiber, or if the chips are relatively small. To combat these hazards, both the '870 Patent and the '974 Patent teach treating the rubber nuggets with a fire retardant. Unfortunately, some fire retardants used in these and other prior art systems tend to wash off, such that traps maintained outdoors may lose their fire retardant characteristics during and after a rain if not properly maintained.
Additionally, though extant systems trap the bullet, they typically do nothing to stabilize them from an environmental hazard standpoint. Thus, expended rounds must periodically be recovered from the trap to prevent heavy metal leaching and associated environmental contamination.
Nor do prior art systems protect or shield spent rounds from incoming rounds. As expended rounds accumulate, the possibility of incoming rounds impacting spent rounds increases, which in turn increases fire, ricochet, and fragmentation hazards. For example, the entire volume of the bullet trap disclosed in U.S. Pat. No. 6,293,552 to Wojcinski et al. (“the '552 Patent”) is exposed to incoming fire. This problem is compounded in traps used with automatic weapons, which are capable of building up a significant mass of spent bullets in a relatively short period of time, increasing the need to periodically “mine” the trap to reclaim spent rounds.
To remove accumulated rounds, many prior art systems, such as the '552 Patent and U.S. Pat. No. 6,000,700 to Nesler et al. (“the '700 Patent”) teach removal via a trap door or similar access panel. Both the '552 Patent and the '700Patent utilize a flowable ballistic material, and intend for a combined volume of ballistic material and spent rounds to flow out of the trap during cleaning. Since rounds will impact the trap at a number of points, however, it is often necessary to remove a substantial volume of the ballistic material in order to ensure adequate cleaning. Furthermore, the mining process is generally burdensome and time consuming.